Conveyor belts have been known for a long time, generally made from rubber or a synthetic material and comprising a flexible inner core.
Various methods have been used in the past to provide the junction between the ends of a conveyor belt that is initially open at both ends, with a view to transforming it into a so-called endless operational conveyor belt. These junction methods are also used for the insertion of new sections in a current conveyor belt, with a view to extending the length of said current belt, for example to follow-up the progress of mining work or to replace a part of the conveyor belt that has been damaged.
Notable among these methods is the vulcanisation of the ends, with a prior operation of baring the core and forming degrees with shapes that complement the two ends of the conveyor belt. Vulcanisation provides excellent results, but it has the disadvantage of the time required to perform it, taking up to 24 hours, which is a definite handicap.
Another method used is gluing with technical glues. As with vulcanisation, it requires a great deal of care to be taken as regards the preparation of the ends, and great rigour as regards the conditions under which the technical glues are applied.
Metal clips mounted on the ends of the conveyor belt and connected to each other by means of a linking and hinging rod passing through the knuckles of the metal clips, mounted on the edge of the ends of the conveyor belt, are another well known method used for joining the ends of conveyor belts. However, this device has problems caused by the wear of the clips and of the linking rods as well as by localised wrenching, which require repairs and increased stopping times of the conveyor belts.
New types of junctions have furthermore been suggested by the applicant of the present application. These junctions are described in detail, for example, in U.S. Pat. Nos. 5,839,571 and 6,601,698. Express reference is made to these patents. In short, these junctions consist of reinforced junction elements made from rubber or synthetic materials, with a general H shape, extending around the ends of the conveyor belt, on either side of the central section of the generally H-shaped junction, one of the flanges having pre-punched holes equipped with cup inserts, and the other flange having pre-punched holes equipped with bush inserts. These holes equipped with cups are placed in staggered rows over quite a large surface in order best to distribute the traction efforts to which the flanges of the junction and the conveyor belt are subjected.
These H-shaped junctions, screwed in the perpendicular direction of the general plane of the junctions, described in U.S. Pat. No. 6,601,698 B2, have turned out to be excellent as far as their strength is concerned.
In addition, it is possible to remove screwed junctions of this type, which allows easy replacement of a damaged section of the conveyor belt, or to extend the length of the conveyor belt with a view to following up the progress of mining work, for example.
However, these junctions, which have solved many problems in certain industries, in particular in heavy extraction industries, for transporting coal, minerals, phosphates and other heavy loose products, still encounter, in certain cases, problems with wrenching of the flanges which, although they are bevelled in the direction of the thickness at the end that is in contact with the conveyor belt, have a thickness that sometimes catches with the scrapers with which these belts are equipped.
Finally, it is desirable to have, for example in order to replace conveyor belts of a given machine of standard model and length, for example in roadworks, earthworks, farming work and similar work, conveyor belts with ends that are prepared for being quickly and easily connected.
Past patent applications have already proposed conveyor belts equipped at their ends with half-junctions with matching shapes. The patents of the prior art GB-A-548 209 by the Dunlop Rubber Company Limited, GB-A-708 461 by Cable Belt Limited and FR-A-1 140 516 by the Dunlop Rubber Company Limited can be mentioned as an example of this.
However, the junction devices provided in these patents of the prior art were difficult to implement and the handling of the ends of the conveyor belt in order to present them for mutual attachment was very complex. Moreover, the attachment means, slats or rods passing through the transverse holes alternately belonging to either one of the ends of the conveyor belt were very difficult to install, in particular in the heavy conveyor belts. Finally, the resistance to traction of these junctions with transverse slats was not satisfactory. Indeed, the transverse slats or rods caused shearing effects in the constituent material, present between the two layers of core placed respectively above and under the transverse holes, which resulted in wear and tear of the junctions.